Process for treating iron and its alloys



USC., 18 1923.,

` W. H. FISHER ET AL.

PROCESS FOR TREATING IRON AND ITS ALLOYS Original Filed May 18. 1920 MS A fron/vg: y.

Patented Dec. 18, 1923.

UNET@ STATES invase? eraan erstes.

'WILLIAM H.r FISHER, OF LOS ANGELES, AND PETER CHAMBMS, OF REDONDO BECE,'

CALIFORNIA.

PROCESS FOR. TREA'IING IRON AND ITS ALLOYS.

Original application filed May 18, 1920, Serial No. 382,290. Divided and this application filed October im,

1920. SeriaDNo. 416,657.

To all whom t may concern.'

Be it known that we, WILLIAM H. FISHER and PETER CHAMBERS, both citizens ofthe United States, residing, respectively, at Los Angeles and Redondo Beach, in the county of Los Angeles and State of California, have invented a new and useful Process for Treating Tron and Its Alloys, of whichrthe following is a specification.

This invention relates to a process or method for treating iron and iron alloys. This process may be carried on in practice by using a suitable furnace, which utilizes a particular liquid hydrocarbon which Will not oxidize the steel used in the furnace. We may employ a furnace using a liquid hydrocarbon which will perform the impregnating process or make the surface of the steel more dense with carbon in a shorter period of time 2C than heretofore, and which impregnating process will be fperformed with uniformity,

will leave no so t spots in the metal, and reduce the cost in operation. l/Ve may further employ a particular liquid hydrocarbon with 25 a specially constructed furnace, `which hydrocarbon forms into a gas having certain properties and which gas escapes after the carbon has been removed from the same, and burns while escaping. The gas which is burning indicatesvthe degree of work being performed in the interior of the furnace, by the color of the burning gas and the heighth to which it glows `or burns. Thus it is possible without the use of artificial 35 'means, as now used, to know at a glance the degree of carbon being absorbed by the steel in the interior of the furnace. V

In practicingr the invention, we preferably provide a special hydrocarbon oil which vis fed into a suitable retort at a pre-arranged speed. This retort connects with the vinterior of a cylindrical ,casing provided with perforations, which latter casing is arranged within a work-holding retort. Suitable heating means heats the retort and in so heating gasiiies the liquid and the gasitied liquid passes through the perforatious and contacts with whatever work may be within the work-holding retort. Gas is allowed to escape through a vent in the cover of the retort after the carbon has been taken from same, and the gas as it escapes burns with a bluish flame. The particular color or change in the bluish color, as Well as the height which .the flame reaches, indicates the amount of carbon that is being absorbed by the steel. It is necessary to determine the amount of carbon absorbed by a metal or metals by direct experiment and to note said experiments and results, so that the height to which the flame burns, as well as its color, may be noted for subsequent work. No fixed .rule can be asserted, for the reason that furnaces differ. The pressure of the gas within a retort, as Well as the nature of the gas, would have its influence and therefore a primary experiment must of necessity be made.

It has been customary to carbonize or easeharden steel by utilizing such carbonizing materials as charred leather, powdered bone, cyanide of potassium, wood and animal charcoal, prussiate of pot-ash and other materials consisting of` mixtures of carbonaceous materials and certain cyanides and nitrates. The steel articles to be impregnated with carbon are first packed in a suitable box after a layer of casehardening material has been placed upon the bottom of said box, the thickness of the layer depending on the size of the pieces to be hardened. Obviously in order to properly caseharden a metal it is necessary that the surface of the parts should be in direct contact with the carbonaceous material, and if the parts should happen to touch one another it is quite likely that the parts thatl touch will be softer at the space where they are in contact. It has been found that if there is not enough carbonizing material in the box the work is also liable to have soft spots. It has been found impossible to properly impregnate steel or make it more dense where considerable depth of carbon is required by packing the articles with bone or vcharcoal in an iron box and sealing on the cover. This is due to the fact that only a` certain amount of carbon is present. and the longer the work is baked, the more there will be in the steel and the less in the charcoal. When au equilibrium is establishedno more carbon will penetrate the metal, and to obtain a greater depth, `the work must be packed in-fresh carbonaceous material and the heating repeated. It has likewise been found very difficult to correctly determine the depth of impregnation of the carbon Within the steel, and various degrees Yof heat have been determined at which points the iron or steel will contain certain amounts of carbon.

The inventors are aware that certain processes have been developed which do not require placing articles to be carbonized in iron CTI boxes packed With carbonaceous material, and that such processes have been developed by Giolitti and by the American Gas lurnace Company. The Giolitti process consists essentially in packing the work with wood charcoal in a cylinder and when heated to carbonizing temperature a current of carbon dioxide is injected into the cylinder. The American Gas Furnace process or method consists in using gas as a carbonizing material and placing the Work in a small revolving, properly heated, cylindrical retort into which the carbonizing gas is injected under pressure. From. the gas the Work absorbs the volatile carbon.

' It is obvious that a furnace of this type using a carbon gas Would be less expensive in operation than the old method of first packing the articles to be impregnated with carbon, as at least three or four operations would be entirely done away with. lt has been found that the use of carbon monoxide While capable of rapid penetration, has an oxidizing effect on steel, and is liable to form a scale that will spoil small Work whichA cannot afterwards be ground. This oxidiz ing e'ect is more pronounced in chromium and manganese steels. Casehardening is mostly performed on small articles which must have a perfectly hard surface and yet be of such internal structure that there is no chance of breaking them when in use. For example, in the making of axles, cups, cones and similar articles. The Giolitti process above mentioned depends upon passing carbon granules into a mulle or Workholding retort under pressure, and the carbon becomes mobile and flows like a liquid in the presence of heat, and in so flowing passes into all insterstices surrounding the Work. This process of course necessitates an accurate handling .and expert attention to details, but it is more rapid than the old method of first packin the articles in boxes. As for the revolving urnace method, While this ensures an even distribution of heat, still the revolving process is liable to dump the different articles within the retort upon each other and if the articles should happen to be gears, to possibly break the teeth of same. With the idea of overcoming the objections now incident to furnaces of this latter type, the inventors have constructed a novel form of voven Which utilizes a particular hydrocarbon fluid which Will not oxidize the stel, thus spoiling small work. The interior of the Work-holding retort is at all times dry; that is to say, water is 'not formed Within the retort upon the heating of the gas, as is ordinarily the case; in fact,

the presence of Weten is highly disastrous in furnaces of this form. Likewise the gas used does not have an oxidizing effect on the alloyed steels, The entire furnace with its 1iquid hydrocarbon is capable of being so adjusted that one attendant can readily perform all the operations necessary andl incident thereto. Furthermore. the apparatus is simple in design and readily accessible.

It will be understood that the use ofthis hydrocarbon liquid and this furnace is for performing the casehardening process only, and does not refer to the quenching or the tempering rocess that is necessary after the steel has been impregnated with carbon. The furnace is made of such a size that it gives a uniform heat throughout and performs its work more rapidly and more uniformly than is possible with any known process on the market today. The carbon removed fromy this hydrocarbon liquid will lind its Way into slots, holes and cavities which would not under ordinary circumstances receive the carbon from the granulated bone or any other solid packing material, and hence .the uniformity of the product is greater. In many cases, lon7 carbon steel treated by this particular process may be substituted for tool steel in machine construction. Furthermore, the percentage of carbon in the gas surrounding the Work can be maintained at a 'permanent figure until the carbon has penetrated to the desired depth of the metal.

The invention hasforfurther objects to provide a process of the character abovementioned, which Will be relatively simple and Ainexpensive in carrying on or practicing or urtherance, taken in conjunction With efliciency, speed, and expediency and general adaptability.

The invention consists in the novel and useful process hereinafter disclosed and finally pointed out in claims.

The improved apparatus and furnace herein disclosed are disclosed and claimed in a parent application for U. S. patent for apparatus for treating iron and iron alloys and process thereof, tiled May 18, 1920, in the United States Patent Otiice, Serial Number 382,290; and the carbonizing compound therein disclosed is claimed in a divisional application under said parent application, said divisionalapplication being executed by us this 30th day of September, 1920, preparatory to filing the same in the U. S. Patent Oilice.

lt will be understood that many variations in detail may be made in departure from the specific definition of the process as Well 'as the apparatus about to be disclosed.

In the drawing:

Figure 1 is a fragmentary elevation, certain parts being shown in section of an improved furnace used in connection with a certain liquid hydrocarbon for casehardenin steel, taken on thel line @a1- m1 Figure 2;

igure 2 is a fragmentary bottom view of the device shown in Figure 1, and taken on the line .r2-x2, Figure 1, and looking in the direction of the appended arrows; and

Figure 3 is a cross sectional view of the device shown in Figure 1 and taken on the line :v3- m3, Figure 1, and looking in the direction of the appended arrows.

Referring with particularity to the drawing, A designates a furnace of which B is the outer casing wall, C heat resisting means, D a work-holding retort co-axially arranged within the furnace A, E a cylindrical perforated casing located in the bottom of the workholding retort, F a sight feed reservoir for holding certain liquids used in connection with the furnace` G means for conducting gas for heating the interior of the furnace, and H a container for holding a liquid hydrocarbon within the perforated cylindrical wall member,-a1l of which elements are used in practicing one embodiment of the invention.

The furnace A is so constructed that all arts of the furnace are readily accessible. Fhe furnace consists essentially in the outer cylindrical casing B provided with a cover member 1 and a base member 2. Within the outer casing B are arranged fire brick or other heat-resisting material C. lThis heatresisting material C is made in segments as shown inv Figure 3. This particular construction overcomes any tendency for the furnace to crack or bulgeV due to excessive heat or excessive. cold incident to cooling. Intermediate the outer periphery4 of the heat-resisting means C and the casing B is a fibrous substance 3 which will not conduct heat. rThe end portions 1 and 2 are likewise provided with heat-resistiner means C', the cover 1 and the base 2 holding the heat-resisting means C in position. In order to ensure the casing B maintaining its form.

a flanged rim 4; is provided at its upper end as at 5 and held in relation thereto by bolt members or screws 6. rlhe lheat-resistingineans C is annular in form in order to accommodate the work-holding retort D, as shown in the drawings. The base member 2 is likewise annular in form and is provided with a downwardly directed flange 7 at its outer edge, which flange is accommodate bolts 8 for holding the outer casing B to said base and flange. Certain of the fire brick or heat-resisting elements l C are provided with semi-conical perforations 9 which likewise extend through the nonconducting heat element 3 and the outer casing B. Disposedwithin a portion of this perforation 9 is -a'pipe'lO connecting with the conducting 'means carrying whatever fluid is to be burned to heat the furnace. The perforation 9 is purposely made in the erforated to drieal in form and has an .end portion as.'

atll slightly beveled as at. 12 on the outer peripheral edge thereof. The lower annu- V,lar heat-resisting means C' is likewise beveled as at 13 on its inner peripheral annular edge. The heat-resisting element C', as well asthe work-holding retort D areinade this way in order that there may be a close cooperation with their respective edges in order to ensure a close fit with little lor no loss of gas or heat. The base member 2 is likewise provided with a flange 14 in order to aid in retaining the workolding retort D in position upon same. Reference to the figures will show that there is a spaced ortion 15 existing between the Work-hol ing retort D and the inner peripheral surface of the heat-resisting elements C. Combustion of gases used in heating the furnace occurs inthis spaced portion 15.

The mea-ns G used in conducting lgas to the interior of the furnace comprises a series of inter-connecting pipe members 16 joined together by elbows. as shown in the figures. Referring to Figure 2 it will be noted that one portion of the means G communicates-With an air supply and the other portion with the source of gas supply. The part that ordinarily is used in forcing air within the pipe members 16 is associated with a blower so as to give the necessary oxygen content to the gas, as well as to create a hot flame within the space 15 of the furnace A. lt is customary to utilize an expansion tank in order to get a constant air pressure. Otherwiseithe-piilsation from the blowerwill affect the heat in the furnace. However. in the particular construction of the furnace shown. it is .not absolutely necessary to use the expansion tank, as the perforation 9 and the space 15- act to a certain extent as an expansion chamber.

The top 17 of the work-holding retort D is provided with a U-shaped or vflanged cover member 18. which cover is provided with a centrally located vent 19. 'l` he cover is likewise provided with gripping ring brackets 20. so that a rod might be run through the perforations 21 in said ring brackets 20 and thecover 18 removed from the end of the work-holding retort D in order to insert work or to remove work from the interior of said retort D. Supported upon the base member 2 as at 22', is a cylindrical casing E having one end as at 23 circiimferentially and outwardly flanged, which flanged portion acts as a foot means lll@ for rigidly holding ai@ Cylindrical Casing n .ing through the wall thereof, and is provided at its opposite end as at with a flanged cover plate 26, which vplate is likewise providedl with a series of perforations 27.

Within' the cylindrical casing E and inV spaced relation thereto is an inverted bucket-shaped member 28 provided with an enlarged hole 29 in what would be the base of said `member 28, and disposed over thehole 29 is a protecting spaced plate 30 supported upon legs 31. A side member 32 of the bucket-shaped element 28 has its end as at 33 beveled as shown-at 34, and the beveled portion rests upon a correspondingly beveledl portion 35a on the inner peripheral annular edge-of the base member 2, so that the member 28 may be always retained in a definite close fitting engagement with the base member 2. l

A plate member 35 covers the open annular portion of the base member 2 and likewise the'openinterior portion of the bucketshaped member 28, and is held in relation' to the base member 2 by means of stay bolts 36. The member 35 is provided with a circumferential lug 37 which forms with the edge to which it is jon, flanged portions 38 and 39, which flanged portion 38 co-operates with the inner peripheral annular Wall of the base member 2. Likewise the lug 37 is provided with perforations at certain ldistances in order to accommodate the stay bolts 36. The member 35 is internally chambered as at 40 to accommodate a cylindrical member 41, and the chamber wall portions 40 of the member 35 are made at a convergent downward angle while the end portions as 42 of the member 41 are correspondingly angled or beveled so as to form a close fit with the side walls of the chambered portions 40. Centrally located and communicating with the interior of the member 35 Vis a perforation 43. Located externally of the furnace A and joined to the casing near one end as at 44 is a bracket arm 45 held in position to the casing B by means of a bolt46. A portion of the bracket 4521s at 47. supports thereon a sight feed reservoir F lof any standard form. Communicating frfom the interior of the sight feed reservoii` l" is a fluid conducting pipe 48. Acrossliead 49 joined to the pipe 48, haswone of its terminals as 50 communieating withiheperforation 43 and with the interior of the member 41. The oppositely directed portion `51, that is, the portion opposite the terminal 50 is provided with a valve cock 52, and a terminal 53 directly opposite the entrance of the conducting means 48 is provided normally with a ca 54.

he furnace ground or flooring by means of aplurality 4of leg members 55 which are joined to the base 2'and held rigidly thereto.

The opera-tion is as follows: The'liquid hydrocarbon is placed within the sight feed reservoir F and a control valve handle 56 is so set that a predetermined quantity of said hydrocarbon lfluid will drop past the sight 57 and into the pipe ticular construction of the perforation 9 v gives the gas and the air a whirling edect within the space 15 and consequently there is a solid mass of flame surrounding the work-holding retort D. The heat from the gas is communicated through the walls of the` work-holding retort D .and thence through the walls and perforations of the member E and finally to the fluid contained within the member 41. This heat causes the hydrocarbon fluid to vaporize and pass upwardly through the hole 29v in the bucketshaped member 28 and from a vaporous stage it passes through perforations 24 and 27 in' the form of a gas into the work-holding retort. The perforations are preferably made small so as to retard the passage of the gas as much as possible. The gas completely fills the work-holding retort D and contacts with the work supported upon the cover plate of the member E. As the carbon is constantly removed from the gas and uniting with the steel one of the products of said gas, which is hydrogen, passes upwardly through the vent 19 and is there ignited and burns with a pale flame. As is before eX- plained, the particular color of this flame indicates the condition of the carburizing of the steel within .the retort. It is customary to note temperature variation by inserting a thermo-couple or by focusing an optical pyrometer successively indifferent parts of the furnace, all of which is unnecessary in i the present furnace.

The work such as gears, axles, etc., is stacked upon the cover plate 26 of the member E and the plate 18 then placed in position covering the work-holding retort..

Ordinarily the carburizing operation requires some twelve hours of time, but with this device it has been found that it will perform the same amount of workl in from three to four hours. .In order to remove the v work means are slipped through the perforations 21 in the brackets 20 attached to the cover 1S and thecover removed and grip-l ping irons may grasp the flanged portions 1of the cover plate 26 and lift the work comletely out of thel work-holding retort. It is a feature of this furnace that practically all air is excluded from same as the hydrocarbon fluid used contains little or no oxygen and the oxygen of the atmosphere is not permitted to come into Contact with the work because the gas rising from the hydrocarbon fluid prevents the air from coming into contact with the work as the work is lifted from the work-holding retort D. Obviously the source of heat supply could be diminished by turning the valve cocks 59 and 60 and the different articles allowed to cool, after which they might again be reheated without using the hydrocarbon fluid and then removed from the worlcholding retort and quenched on a rising heat, which is most desirable. It is commonly known that the actual carburization is due to the hot gases which are either liberated by the casehardening compound or formed by the reaction between the occluded air and the carbon. It is also well-known that the active casehardening reagent is a gas or a mixture of gases and that even whena powder is used that it is the gas liberated from the hot powder and not the solid itself that performs the work. Consequently the use of a particular liquid hydrocarbon which is utilized in this furnace readily performs its work in a most eflicient and quick manner without waste. As to the reason why this gas does not make deposits of carbon within the perforations 24 and 27 or why it does not oxidize the steel, or why it has no oxidizing effect on chromium and other alloyed steels is not known by the inventors.

Reference to Figure l shows that the hy.

drocarbon fluid may be readily drained from the member il by turning the valve cock 52 and closing the handle 56 which controls the sight feed reservoir. 'lhe plate 30 provided with the legs 3l covering the hole 29 of the member 28 is placed there for the express purpose of preventing any foreign substance, if any there be, from falling upon the liquid hydrocarbon contained within the member el and forming a surface coating upon said liquid that might prevent its ready vaporization. lf it were desired to clean the internal parts ofthe furnace a removal of the stay bolts 36 would allow the plate 35 to be removed from the base member 2. rlhis will allow the cross head A19 to be released from the perforation 43 and the plate 35 and the member al withdrawn from position. Thus the interior of the bucketshaped member 28 might be cleaned. By removing the cover 18 the cylindrical member E might be drawn through the worlcliolding retort D and the member 28 likewise removed. lf desired, the work-holding retort D could be drawn through the annular space formed by the heat-resisting elements C and C and a new work-holding retort placed therein. Thus it will be dbserved that all parts are readily accessible for renewal or for repairs.

It has been found byexperiment that a liquid hydrocarbon which consists essentially in using in proportion by volume pine tar 40%, turpentine 20% and linseed oil 40%, will most efficiently when gasified carburize or caseharden steel. A combination of those particular elements to form the hydrocarbonlluid will perform all the functions that have been above attributed to said hydrocarbon fluid. It is manifest that many variations and changes may be made with respect to the disclosure of the foregoing furnace and details of process used in connection with the particular chemical constituents of the l1ydrocarbon fluid just described, within afair interpretation of the invention.

Having thus disclosed our invention, we claim and desire to secure by Letters Patent:

1. Illhe method of carburizing steel and similar metals and alloys thereof when heated to a carburizing temperature in a work-holding retort of l a furnace, which consists in causing a hydrocarbon fluid to -flow into a portion of said retort in such a manner as to be subjected successively tof an increasing heat, whereby a portion of the fluid expands into a vapor, then retarding the movement of the vapor, and finally distributing same around the work in the form of a carbonizing gas.

2. The method of carbonizing steel and similar metals and alloys thereof, which consists in subjecting a. hydrocarbon fluid to a veryin heat so as to vaporiae a portion. thereo subjecting the vapor to an increased heat thereby forming a nascent gas, then retarding and evenly distributing the gas in its flow into the work-holding retort.

3. rllhe method of carbonizing steel and similar metals and alloys thereof, which consists in subjecting a hydrocarbon iluid to a varying heat so as to vaporize a portion thereof, allowing the vapor to expand, then subjecting the expanding vapor to an increased heat thereby forming a nascent gas, then retarding and evenly distributing the gas in its flow into the workholding retort where carbon content is combined withthe metal.

fl. The method of carbonizing steel and like' metals when heated to a carburizing temperature in a work-holdin retort of a, furnace, which consists causing a hydrocarbon fluid to flow into portion of said retort -in such a manner as to be subjected successively to an increasing heat whereby a portion of the fluid expands into a vapor,

las

carbon fluid to flow into a portion of said retort in such a manner as to be subjected successively to an increasing heat whereby a portion ot the Huid expands into a vapor, then retarding the movement of the vapor, distributing same around the Work in the form of a carbonizing gas, and finally burning the gas residue from which carbon has f 6. The process of impregnating the 'faces of iron, steel and its alloys with carbeen taken in the form of a taper outside the furnace, and by observation of the combustion of the residue determining the proportion Aof a. carbon being,r combined With the metal. r

sur-

bon, and indicating the degree and condition oi impregnation thereof, which consists, when the iron, steel and its alloys have been heated to carbonizing; temperature, in gasi'fying a liquid hydrocarbon in the presence of the work to be carbonized,l and then allowing the residue gas from which the carbon has been removed to escape and burn while so escaping, the height and color inluence of the heat present for applicationl to the metal, then burning the residue of the gas as it escapes and by observation of the combustion ofthe residue determining the proportion of carbon being combined withthe metal.

8. The method of carbonizing steel and similar metals and alloys thereof, which consists in subjecting a hydrocarbon fluid to a varyingheat so as to first vaporize a portion thereof,' allowing the vapor to expand, then subjectingl the expanded vapor t0 an increased heat, thereby eausingdisassociation of the component compounds of the hydrocarbon Huid, then retarding and evenly distributing the gas in its flow into the work-holding retort, Where carbon content is combined with the metal.

In testimony whereof we have signed our names to this specification in the presence of a subscribing witness.

WiLLrAM n. msnen. PETER CHAMBERS. Witness:

MHDRED LEACH. 

